1. Field of the Invention
The present invention relates to a display device, a data processing device and a computer readable medium.
2. Description of Related Art
In recent years, when performing presentation, there is used a method for creating document data for presentation by using application software such as Power Point (registered trademark) on a PC (Personal Computer) and displaying slides of the document data per page.
When performing presentation, apart to be focused in an image is enlarged to be displayed in many cases. As a technique for enlarging a part of display information, for example, there is suggested a display information enlarging method for a mobile terminal that is preparing character strings in a standard size and character strings in an enlarged size, converting a character string which is selected among the displayed character strings in the standard size into a character string in the enlarged size corresponding to the character string, and displaying the converted character string (see Japanese Patent Application Laid Open Publication No. 2006-119229).
When presentation is performed by using a tablet terminal which is not equipped with the application software that created document data, the presentation is performed by converting the document data into an image file in a JPEG (Joint Photographic Experts Group) format for each page in the PC, and thereafter transmitting the JPEG file for each page to the tablet terminal to display the image of each page on the tablet terminal. In the tablet terminal, display of an image of next page or previous page and enlargement or reduction of the image is instructed by user's operation.
Here, a general operation in a case where an image is displayed on a tablet terminal will be described with reference to FIG. 13. An image 40 for one page displayed on the tablet terminal includes a figure (circle graph) 41 and a photograph 42. When the FIG. 41 is enlarged to be displayed, an operation (pinch operation) is performed, the operation being touching the lower left 43 and the upper right 44 of the FIG. 41 with fingers at the same time and directly increasing the space between the fingers until the FIG. 41 is displayed in a desired size. In the example of FIG. 13, by moving the finger touching the upper right 44 of the FIG. 41 in the arrow Z direction, the FIG. 41 is enlarged in accordance with the movement of the finger.
However, when instructing the enlargement by the pinch operation on a screen of the tablet terminal, there has been a problem that the screen flickers and is difficult to be seen since the JPEG image is enlarged and redrawing is performed for the entire screen every time the movement of finger is detected.
In addition, when the user is not accustomed to the operation, the enlargement operation is performed in several steps, the image is excessively enlarged to need a reduction operation in reverse, or such like, and thus, the pinch operation needs to be performed a plurality of times, leading to bad operability.
Furthermore, since the user performs an operation by moving a hand above the screen in the tablet terminal, the hand covers the screen during the operation, which is visually undesirable.